β-fructofuranosidases are enzymes that recognize fructose in sucrose and have the activity of hydrolyzing the sucrose into fructose and glucose (sucrose hydrolysis activity). Some β-fructofuranosidases have the activity of transferring the fructose formed by hydrolysis to sucrose (fructose transfer activity) and form a trisaccharide kestose in which one molecule of glucose is bonded to two molecules of fructose.
Among such kestoses, 1-kestose retains sweetness similar to sucrose (sugar) and is known as a useful oligosaccharide, for example, because this saccharide has approximately half of the calorie of sugar while offering approximately ⅓ of the sweetness of sugar, rarely increases blood glucose levels when ingested, and exhibits antiallergic functions (Patent Literature 1). For example, a β fructofuranosidase derived from Aspergillus niger and a β fructofuranosidase variant containing an amino acid mutation in the amino acid sequence thereof are disclosed (Patent Literature 2) as β-fructofuranosidases that form 1-kestose.